One gunshot struck the windscreen of the bus, which was on its way to pick up the team from Bielefeld railway station ahead of their DFB-Pokal clash with the second-division side on Monday evening.
Hertha posted a photo of the damage to the windscreen on Twitter and appealed for witnesses. At the time, only the bus driver was on board.
The club’s director of sport Michael Preetz told Sport1 television: “It was a gunshot, but we do not know what the motivation was behind it.
“The bus driver called the police immediately and they are now searching for the criminal.
“A motorcyclist overtook the bus first and stuck his fist up threateningly towards our bus driver and then drove at him around a roundabout and drew a pistol.
“Whether it was because he thought the team was on the bus or not, we cannot say. That would be pure speculation.”
Monday night’s cup game is due to go ahead as planned.
“The team have seen the gunshot damage, but the biggest shock was to our bus driver,” added Preetz.
A Bielefeld police statement said: “This afternoon the bus was on its way from the team hotel in Marienfeld to the Bielefeld main train station to pick up the team.
“On the way there, a motor bike driver dressed in black overtook the bus and a shot was then fired on the bus which collided with the windscreen. The window was lightly splinted. Thankfully no one was hurt.
“Within my knowledge my colleagues talked to the bus driver and asked him. He said he could park the bus without being in any danger at a nearby bus stop.
“There was some kind of provocation by the motor biker earlier today so that we assume that the biker saw the bus as the Hertha BSC bus.”
On it being a planned attack, the statement continued: “That will be the focus of our investigation which we will continue with pressure.
“We take the situation very serious; we quickly want to find out why exactly the motorbike driver did what he did.”